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Open Access Research article

Significance of fractional exhaled nitric oxide in chronic eosinophilic pneumonia: a retrospective cohort study

Ji Young Park12, Taehoon Lee12, Hongyeul Lee12, Yeon Joo Lee12, Jong Sun Park12, Young-Jae Cho12, Ho Il Yoon12, Jae Ho Lee12 and Choon-Taek Lee12*

Author Affiliations

1 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Respiratory Center, Seoul National University Bundang Hospital, 173-82 Gumi-Ro, Bundang-Gu, Seongnam 463-707, Republic of Korea

2 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea

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BMC Pulmonary Medicine 2014, 14:81  doi:10.1186/1471-2466-14-81

Published: 12 May 2014

Abstract

Background

Chronic eosinophilic pneumonia (CEP) is characterized by chronic eosinophilic infiltration of the lung. It is dramatically responsive to corticosteroid treatment, but symptoms and radiopacities recur frequently after tapering or discontinuing the medication. Fractional exhaled nitric oxide (FeNO) is a well-known noninvasive marker of eosinophilic airway inflammation. The aim of this retrospective cohort study was to investigate the relationships of FeNO with peripheral eosinophilia and the clinical state of CEP and its validity for predicting exacerbation of CEP.

Methods

Standard clinical and laboratory parameters, peripheral eosinophil percentage and count, and FeNO level were measured in 18 patients with CEP at several assessment points over 1 year.

Results

FeNO level was positively correlated with peripheral eosinophil count (r = 0.341, P = 0.005) and percentage (r = 0.362, P = 0.003). The median (IQR) FeNO levels were 79 (41–88) and 35 (26–49) ppb in uncontrolled (13/74 measurements) and controlled (61/74 measurements) CEP, respectively (P = 0.010). The FeNO level of 66.0 ppb showed the largest area under the curve (0.835) for predicting exacerbation of CEP (sensitivity = 0.80, specificity = 0.84).

Conclusion

FeNO may be useful for monitoring eosinophilic parenchymal inflammation and determining the appropriate corticosteroid dose in CEP.

Keywords:
Chronic eosinophilic pneumonia; Fractional exhaled nitric oxide; Biomarker; Corticosteroid